Pump Stage Assembly, External Gear Pump, Use Of A Pump Stage Assembly and Vehicle Transmission

ABSTRACT

A pump stage assembly for supplying lubricating oil, comprising: at least two pump suction stages and at least one pump pressure stage. The pump suction stages and the pump pressure stage are spaced apart from one another in a pump housing PG and have a common drive shaft. The pump suction stages are formed by a first assembly of at least three intermeshing external gearwheels and wherein the pump pressure stage is formed by a second assembly of two intermeshing external gearwheels. Here at least two respective tooth center points of the first external gearwheel assembly and the respective tooth center points of the second external gearwheel assembly are arranged in a common plane E-E which intersects the pump housing PG in a longitudinal direction.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a U.S. national stage of Application No. PCT/EP2020/066834 filedJun. 17, 2020. Priority is claimed on German Application No. DE 10 2019208 847.3 filed Jun. 18, 2019 the content of which is incorporatedherein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present disclosure relates to a pump stage assembly for supplyinglubricating oil to at least one consumer. The present disclosurefurthermore concerns a use of such a pump stage assembly for supplyinglubricating oil to an at least one-stage or two-stage transmission fordriving a vehicle, in particular an electric vehicle, and a vehicletransmission.

2. Description of the Related Art

In vehicles, so-called wet sump lubrication systems or dry sumplubrication systems are used for lubricating internal combustion enginesand transmissions.

Here, a dry sump lubrication system is normally only used in sportscars, off-road vehicles, and motorcycles. It provides lubrication evenat extreme turning speeds or on sloping off-road travel, in that itprevents lubricating oil from flowing out of a region of an intakeconnector of an oil pump under high centrifugal forces or atcorresponding sloping attitudes. This is guaranteed since, as well as anoil pan which is kept dry (in contrast to a wet sump lubricationsystem), a separate oil tank is also used to store the lubricating oil.The oil pan, which is kept dry is also referred to as an oil sump, alsoknown as a dry sump, from which usually a mixture of lubricating oil andair is drawn in.

Because of a smaller volume of such an oil pan, a dry sump lubricationsystem offers greater ground clearance so that e.g. an engine can beinstalled lower, which is in turn associated with a lower center ofgravity—a feature which benefits the above-mentioned sports cars oroff-road vehicles.

A dry sump lubrication system comprises one or more pump suction stagesfor delivering the lubricating oil from the oil sump to the oil tank,and one or more pump pressure stages for delivering the lubricating oilfrom the oil tank to a consumer. The delivery volume of the pumppressure stages is always lower than the delivery volume of the pumpsuction stages.

SUMMARY OF THE INVENTION

It is an object of one aspect of the present invention to improve a drysump lubrication system.

One aspect of the invention is a pump stage assembly. One aspect of theinvention is protection for a multiple action, external gear pump withsuch a pump stage assembly, a use of such a pump stage assembly forsupplying lubricating oil to an at least one-stage or two-stagetransmission for driving a vehicle, in particular an electric vehicle,and a vehicle transmission with such a pump stage assembly. Advantageousembodiments of the invention form the subject matter of the dependentclaims.

A pump stage assembly is proposed for supplying lubricating oil to atleast one consumer. The pump stage assembly comprises:

-   -   at least two pump suction stages for drawing in a lubricating        oil from a first oil container functioning as a dry sump, and        for delivering the lubricating oil to a second oil container        functioning as an oil tank, and    -   at least one pump pressure stage for drawing in the lubricating        oil from the second oil container and delivering it to the        consumer.

The pump suction stages and the pump pressure stage are arranged spacedapart from one another in a pump housing and have a common drive shaft.

The pump suction stages are formed by a first assembly of at least threeintermeshing external gearwheels which lie in a first plane. The pumppressure stage however is formed by a second assembly of twointermeshing external gearwheels, wherein the first plane and the secondplane lie parallel to one another.

Via a first inlet, a first delivery volume flow can be drawn in from afirst region of the first oil container by a first pump suction stage,and via a second inlet, a second delivery volume flow can be drawn infrom a second region of the first oil container by a second pump suctionstage. The two delivery volume flows intermix in the pump housing beforethey reach the second oil container via a respective outlet.

It is furthermore proposed that at least two of the respective toothcenter points of the first external gearwheel assembly and therespective tooth center points of the second external gearwheel assemblyare arranged in a common third plane that intersects the pump housing ina longitudinal direction and lies orthogonally to the first and secondplanes.

The proposed pump stage assembly advantageously allows implementation ofa dry sump system with only five external gearwheels. The proposed pumpstage assembly constitutes a very compact pump solution. The number ofrotating components is kept to a minimum, which is associated with areduction in friction losses. Also, weight is saved.

In principle, these external gearwheel assemblies can be expandedaccordingly as required.

In one embodiment of the present invention, as well as at least two pumpsuction stages, at least two pump pressure stages are provided that areformed by the second assembly of at least three intermeshing externalgearwheels, wherein the at least two of the respective tooth centerpoints of the first external gearwheel assembly and at least two of therespective tooth center points of the second external gearwheel assemblyare arranged in the common plane.

Here, via a first inlet, a first delivery volume flow can be drawn outof the second oil container or oil tank by a first pump pressure stage,and via a second inlet, a second delivery volume flow can be drawn in bya second pump pressure stage. The two delivery volume flows intermix inthe pump housing before they reach the respective consumer via arespective outlet.

The proposed embodiment advantageously allows implementation of a drysump system with only six external gearwheels. This embodiment alsoconstitutes a very compact pump solution in which the number of rotatingcomponents is kept to a minimum.

According to a further, particularly advantageous aspect of the presentinvention, the respective tooth center points of all gearwheels of thefirst external gearwheel assembly and the respective tooth center pointsof all gearwheels of the second external gearwheel assembly are arrangedin said plane. This allows overall an even more compact pump solution.

It is furthermore proposed that the first oil container and/or thesecond oil container form an oil reservoir in the interior of an atleast one-stage or two-stage transmission for driving a vehicle, inparticular an electric vehicle.

According to one aspect of the present invention, the pump stageassembly is configured as part of a plug-in pump solution forarrangement on an at least one-stage or two-stage transmission fordriving a vehicle, in particular an electric vehicle, wherein theplug-in pump solution is flanged to a housing of the transmission andprotrudes into the housing. The plug-in pump solution may advantageouslybe configured as a substantially cylindrical body, wherein the pumphousing forming the cylindrical body is at least partially or suitablyat least mostly injection-molded from a plastic.

According to one aspect of the present invention, a hydraulic connectionof the pump suction stages and/or the at least one pump pressure stageto the transmission oil reservoir is designed radially to the respectiveportion of the pump housing. This allows an even more compact pumpsolution. Here, a hydraulic connection to the pressure side of the atleast one pump pressure stage may be provided on the face of the end ofthe pump housing protruding into the transmission housing.

According to one aspect of the present invention, a hydraulic connectionto the suction side of the pump suction stages may be provided on a faceof an end of the pump housing protruding into the transmission housing.

According to one aspect of the present invention, a hydraulic connectionto the pressure side of the pump suction stages and to the suction sideof the at least one pump pressure stage may be provided on the face ofthe end of the pump housing protruding into the transmission housing.

According to one aspect of the present invention, the common drive shaftmay be driven by electric motor and/or mechanically.

Furthermore, a multiple action, external gear pump with a pump stageassembly of the type described above is proposed.

Furthermore, use of the pump stage assembly described above is proposedfor supplying lubricating oil to an at least one-stage or two-stagetransmission for driving a vehicle, in particular an electric vehicle.

It is also proposed to use the pump stage assembly for cooling anelectric motor driving the electric vehicle.

In addition, a vehicle transmission is proposed for driving a vehicle,in particular an electric vehicle, wherein the vehicle transmission hasa pump stage assembly of the type described above.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantageous developments of the present invention will emergefrom the dependent claims and from the following description ofpreferred embodiments. The drawing shows schematically:

FIG. 1 is a first gearwheel assembly ZA₁ forming two pump suctionstages, and combined therewith a second gearwheel assembly ZA₂ formingtwo pump pressure stages;

FIG. 1A the first gearwheel assembly ZA₁ shown in FIG. 1 in an enlargeddepiction;

FIG. 2A is a pump housing PG with the two gearwheel assemblies ZA₁, ZA₂shown in FIG. 1;

FIG. 2B is cross section along line A-A of the pump housing PG shown inFIG. 2A;

FIG. 3 is a plug-in pump solution;

FIG. 4 is a plug-in pump solution;

FIG. 5 is a plug-in pump solution;

FIG. 6 is an illustration of gearwheel designs; and

FIG. 7 an illustration of delivery flows.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

FIG. 1 illustrates a pump stage assembly 2 as part of a multiple action,external gear pump that serves firstly for supplying lubricating oil toan at least a one-stage or two-stage vehicle transmission V₁ for drivingan electric vehicle, and secondly for cooling an electric motor V₂ fordriving the electric vehicle, which motor forms a drive unit with thevehicle transmission V₁.

The pump stage assembly 2 comprises two pump suction stages 4, 6 fordrawing in a lubricating oil from a first oil container 24, functioningas a dry sump, and for conveying the lubricating oil to a second oilcontainer 26 (the actual oil container or oil tank), and two pumppressure stages 8, 10 for drawing in the lubricating oil from the secondoil container 26 and delivering it to the two consumers V₁, V₂.

The pump stage assembly 2 is part of an at least substantiallycylindrical plug-in pump solution, which is flanged to a housing 62, 64of the vehicle transmission, wherein the plug-in pump solution protrudesinto the housing 62, 64 (see FIG. 3, FIG. 4, FIG. 5). The pump housingPG forming the cylindrical body is advantageously injection-molded froma plastic.

The pump suction stages 4, 6 and the pump pressure stages 8, 10 arearranged spaced apart from one another in the pump housing PG and have acommon drive shaft 56. This drive shaft 56 is driven by an electricmotor (E-motor) M in the context of the embodiments proposed here. Inprinciple however, the plug-in pump solutions could also be drivenpurely mechanically.

The pump suction stages 4, 6 are formed by a first assembly ZA₁ of threeintermeshing external gearwheels 12, 14, 16, whereas the pump pressurestages 8, 10 are formed by a second assembly ZA₂ of three intermeshingexternal gearwheels 18, 20, 22. The external gearwheel assembly ZA₁ liesin a first plane, and the external gearwheel assemblies ZA₂ lie in asecond plane parallel thereto. FIG. 2 illustrates a pump housing PG witha housing part 50 which receives both the two external gearwheelassemblies ZA₁, ZA₂ and also the drive shaft 56 and two axles 58, 60.The drive shaft 56 extends through the gearwheels 12, 18 and drivesthese, while the axle 58 extends through the driven gearwheels 14, 20and the axle 60 through the driven gearwheels 16, 22. With acorresponding design, instead of the axles 58, 60, shafts 58, 60 may beprovided. The housing part 50 is joined to a first housing cover 52 anda second housing cover 54 (see FIG. 2). The pump housing PG, 50, 52, 54is furthermore combined with the above-mentioned electric motor M, whichdrives the drive shaft 56 on which the two driving gearwheels 12, 18 arearranged.

The respective tooth center points ZM₁, ZM₂, ZM₃ of all gearwheels ofthe first external gearwheel assembly ZA₁ and the respective toothcenter points ZM₄, ZM₅, ZM₆ of all gearwheels of the second externalgearwheel assembly ZA₂ are arranged in a common third plane E-E whichintersects the pump housing PG in a longitudinal direction orlongitudinal extent X-X (see FIG. 2). The plane E-E lies orthogonally tothe above-mentioned first and second planes of the respective externalgearwheel assembly ZA₁, ZA₂.

Depending on the fill level, the lubricating oil or—and this is normallythe case—only a mixture of lubricating oil and air is drawn in via twointake lines 28, 30, which each protrude into a respective one of tworegions 24 _(I), 24 _(II) of the dry sump 24, which is divided by a wallW. The wall W dividing the dry sump 24 helps evacuate the dry sump 24,because the dry sump 24 must be kept as dry or empty as possible in allvehicle positions.

The intake line 30 leads to a first pump suction stage suctionconnection SE_(I) of the first pump suction stage 4 formed by the twogearwheels 12, 14, while the suction line 28 leads to a second pumpsuction connection SE_(II) of the second pump suction stage 6 formed bythe two gearwheels 12, 16. A line 32 leads from the first pump suctionstage pressure connection SA′, also formed by the two gearwheels 12, 14,to the oil tank 26. Similarly, a line 34 leads from the second pumpsuction stage pressure connection SA_(II), also formed by the twogearwheels 12, 16, to the oil tank 26 (see FIG. 1a ). Alternatively, theline 32 may also open into the line 34, which then opens in the oil tank(see FIG. 1).

Via a suction line 36, the lubricating oil is then conveyed firstly viaa first pump pressure stage suction connection DE′ (see intake line 38,which branches from the intake line 36 and leads to the pump pressurestage suction connection DE_(I)) and a first pump pressure stagepressure connection DA_(I) of the first pump pressure stage 8—eachformed by the two gearwheels 18, 20—and a line 42 to the vehicletransmission V₁. Secondly, the lubricating oil is also conveyed via asecond pump pressure stage suction connection DE_(II) and a second pumppressure stage pressure connection DA_(II) of the second pump pressurestage 10—each formed by the two gearwheels 18, 22—and a line 42 to theelectric motor V₂.

In a proposed first embodiment of the plug-in pump solution (see FIG.3), an oil tank 26 is formed in the interior of the transmission housing62, 64. A single one or two pump pressure stage(s) DS is/are arrangedbetween the electric motor M, arranged on the transmission wall side,and two pump suction stages SS. The hydraulic connection of the suctionside of the pump pressure stage(s) DS (see intake A_(DS)) firstly, andof the pressure stage (see outlet A_(SD)) of the pump suction stages SSsecondly, to the oil tank 26 are each designed radially to therespective portion of the pump housing PG. The pump pressure stage(s) DSis/are accordingly sealed circumferentially against the pump suctionstages SS (see seal DI). A hydraulic connection of the pump plug-insolution to a dry sump 24 (separate therefrom) firstly, and to the twoabove-mentioned consumers secondly, is provided in each case on the faceof the pump end protruding into the transmission housing 62, 64 (seeintake A_(SS1), intake A_(SS2) of the respective suction stage SS andoutlet A_(DD1), outlet A_(DD2) of the respective pressure stage DS).

Alternatively, in a proposed second embodiment of the plug-in pumpsolution (see FIG. 4), a dry sump 24 is formed in the interior of thetransmission housing 62, 64. Two pump suction stages SS are arrangedbetween an electric motor M, arranged on the transmission wall side, andtwo pump pressure stages DS. The hydraulic connection of the two pumpsuction stages SS (see intake A_(SS1), intake A_(SS2)) to the dry sump24 is in each case designed radially to the pump housing PG. The pumppressure stages DS are accordingly sealed circumferentially against thepump suction stages SS (see seal DI). A hydraulic connection of theplug-in pump solution to an oil tank 26 (separate therefrom) firstly,and to the two above-mentioned consumers V₁, V₂ secondly, is provided ineach case on the face of the pump end protruding into the transmissionhousing 62, 64 (see pressure-side outlet A_(SD) of the pump suctionstages SS, intake A_(DS) of the pump pressure stages DS, pressure-sideoutlets A_(DD1), outlet A_(DD2) of the pump pressure stages DS).

In a proposed third embodiment of the plug-in pump solution however (seeFIG. 5), both an oil tank 26 and a dry sump 24 _(I), 24 _(II), which isdivided by a wall W, are formed in the interior of the transmissionhousing 62, 64. The oil tank 26 is furthermore sealed accordinglyagainst the dry sump 24 (see seal DI). Two pump suction stages SS arearranged between an electric motor M, arranged on the transmission wallside, and two pump pressure stages DS. The hydraulic connection of thetwo pump suction stages SS (see intake A_(SS1), intake A_(SS1) of thepump suction stages SS) to the dry sump 24 _(I), 24 _(II) firstly, andof the two pump pressure stages DS to the oil tank 26 secondly (intakeA_(DA1), intake A_(DA2) of the pump pressure stages DS), are eachdesigned radially to the pump housing PG. The hydraulic connection ofthe pressure-side outlet A_(SD) of the two pump suction stages SS alsoleads into the oil tank 26, radially with respect to the pump housingPG. The pump pressure stages DS are accordingly sealed circumferentiallyagainst the pump suction stages SS (see seal DI). A hydraulic connectionof the plug-in pump solution to the two above-mentioned consumers V₁, V₂is provided in each case on the face of the pump end protruding into thetransmission housing 62, 64 (see outlet A_(DD1), outlet A_(DD2) of thepump pressure stages DS).

The common feature of all these embodiments is that a motor electronicunit ME is arranged outside the transmission housing 62, 64 (see FIG. 3,FIG. 4, FIG. 5, in each case on the right of the flange connection).This allows firstly simple electrical contacting of the electric motoror motor electronic unit ME, and secondly a corresponding heat exchangefrom the motor electronic unit ME to the environment.

FIG. 6 illustrates a design of three intermeshing external gearwheelsforming two pump suction stages or pump pressure stages, whereinpreferably the middle gearwheel is the driven gearwheel. All threegearwheels of this external gearwheel assembly have the samecross-sectional geometry, i.e. also the same number of teeth. The twoouter gearwheels also have the same axial distance from the middlegearwheel. Only the right-hand gearwheel for example has a shorterlongitudinal extent than the other two gearwheels. In principle, theseaxial spacings could also be different. Also, the number of teeth of thetwo outermost external gearwheels could be set differently from that ofthe inner external gearwheel.

FIG. 7 illustrates schematically as an example a division andintermixing of delivery flows, as formed firstly with respect to the twopump suction stages (see ZA₁) and secondly with respect to the two pumppressure stages (see ZA₂) within the pump housing PG. Whereas the twopump suction stages convey an air flow or oil-air flow from the dry sump24 _(I), 24 _(II) (region 24 _(I), region 24 _(II)) into the oil tank26, the two pump pressure stages each convey an oil flow from the oiltank 26 to the respective assigned consumer V₁, V₂. The individualthicknesses of the arrows qualitatively illustrate a correspondingdelivery volume flow. In principle, the respective inflows and outflowsof the individual pump stages may be established as required, inparticular via a corresponding design of the external gearwheels (forthis, see the individual different gearwheel lengths in FIG. 7).

The plug-in pump solutions described in the context of this disclosureeach allow a very compact pump solution suitable for the describedflanging to the vehicle transmission V₁. The number of rotatingcomponents is kept to a minimum, which is associated with a reduction infriction losses. Also, weight is saved.

The plug-in pump solutions described each allow implementation of a drysump system with only six external gearwheels.

It is also pointed out that the exemplary embodiments shown are merelyexamples which in no way restrict the scope of protection, theapplications or design. Instead, the above description gives a personskilled in the art a guideline for the realization of at least oneexemplary embodiment, and various changes can be made here, inparticular with regard to the function and arrangement of the componentparts described, without departing from the scope of protectionresulting from the claims and feature combinations equivalent thereto.

Thus, while there have shown and described and pointed out fundamentalnovel features of the invention as applied to a preferred embodimentthereof, it will be understood that various omissions and substitutionsand changes in the form and details of the devices illustrated, and intheir operation, may be made by those skilled in the art withoutdeparting from the spirit of the invention. For example, it is expresslyintended that all combinations of those elements and/or method stepswhich perform substantially the same function in substantially the sameway to achieve the same results are within the scope of the invention.Moreover, it should be recognized that structures and/or elements and/ormethod steps shown and/or described in connection with any disclosedform or embodiment of the invention may be incorporated in any otherdisclosed or described or suggested form or embodiment as a generalmatter of design choice. It is the intention, therefore, to be limitedonly as indicated by the scope of the claims appended hereto.

1.-16. (canceled)
 17. A pump stage assembly configured to supply a lubricating oil to at least one consumer, comprising: a pump housing; at least two pump suction stages formed by a first external gearwheel assembly of at least three intermeshing external gearwheels that lie in a first plane and configured to: draw in the lubricating oil from a first oil container functioning as a dry sump, and deliver the lubricating oil to a second oil container functioning as an oil tank; and at least one pump pressure stage formed by a second external gearwheel assembly of two intermeshing external gearwheels which lie in a second plane and configured to: draw in the lubricating oil from the second oil container, and deliver the lubricating oil to a consumer, wherein the at least two pump suction stages and the at least one pump pressure stage are arranged spaced apart from one another in the pump housing and have a common drive shaft, wherein the first plane and the second plane lie parallel to one another, wherein at least two respective tooth center points of the first external gearwheel assembly and respective tooth center points of the second external gearwheel assembly are arranged in a common plane that intersects the pump housing in a longitudinal direction and lies orthogonal to the first and second planes.
 18. The pump stage assembly as claimed in claim 17, wherein at least two pump pressure stages are provided formed by the second assembly of at least three intermeshing external gearwheels, wherein the at least two respective tooth center points of the first external gearwheel assembly and at least two of the respective tooth center points of the second external gearwheel assembly are arranged in the common plane.
 19. The pump stage assembly as claimed in claim 17, wherein the respective tooth center points of all gearwheels of the first external gearwheel assembly and the respective tooth center points of all gearwheels of the second external gearwheel assembly are arranged in the common plane.
 20. The pump stage assembly as claimed in claim 17, wherein the first oil container and/or the second oil container forms an oil reservoir in an interior of an at least one-stage or two-stage transmission for driving a vehicle.
 21. The pump stage assembly as claimed in claim 17, wherein the pump stage assembly is configured as part of a plug-in pump solution for arrangement on an at least one-stage or two-stage transmission for driving a vehicle, wherein the plug-in pump solution is flanged to a transmission housing of the transmission and protrudes into the transmission housing.
 22. The pump stage assembly as claimed in claim 21, wherein the plug-in pump solution is configured as a substantially cylindrical body.
 23. The pump stage assembly as claimed in claim 22, wherein a hydraulic connection of the pump suction stages and/or the at least one pump pressure stage to an oil reservoir is designed radially to the respective portion of the pump housing.
 24. The pump stage assembly as claimed in claim 23, wherein a hydraulic connection to a pressure side of the at least one pump pressure stage is provided on a face of an end of the pump housing protruding into the transmission housing.
 25. The pump stage assembly as claimed in claim 24, wherein a hydraulic connection to a suction side of the pump suction stages is provided on the face of the end of the pump housing protruding into the transmission housing.
 26. The pump stage assembly as claimed in claim 24, wherein a hydraulic connection to the pressure side of the pump suction stages and to a suction side of the at least one pump pressure stage is provided on the face of the end of the pump housing protruding into the transmission housing.
 27. The pump stage assembly as claimed in claim 17, wherein the first oil container is divided into at least two regions by at least one wall.
 28. The pump stage assembly as claimed in claim 17, wherein the common drive shaft is driven by an electric motor and/or mechanically.
 29. A multiple action, external gear pump having a pump stage assembly configured to supply a lubricating oil to at least one consumer, comprising: a pump housing; at least two pump suction stages formed by a first external gearwheel assembly of at least three intermeshing external gearwheels that lie in a first plane and configured to: draw in the lubricating oil from a first oil container functioning as a dry sump, and deliver the lubricating oil to a second oil container functioning as an oil tank; and at least one pump pressure stage formed by a second external gearwheel assembly of two intermeshing external gearwheels which lie in a second plane and configured to: draw in the lubricating oil from the second oil container, and deliver the lubricating oil to a consumer, wherein the at least two pump suction stages and the at least one pump pressure stage are arranged spaced apart from one another in the pump housing and have a common drive shaft, wherein the first plane and the second plane lie parallel to one another, wherein at least two respective tooth center points of the first external gearwheel assembly and respective tooth center points of the second external gearwheel assembly are arranged in a common plane that intersects the pump housing in a longitudinal direction and lies orthogonal to the first and second planes.
 30. The pump stage assembly as claimed in claim 17, wherein the pump stage assembly supplies lubricating oil to an at least one-stage or two-stage transmission for driving a vehicle.
 31. The pump stage assembly as claimed in claim 28, wherein the pump stage assembly is configured to cool an electric motor driving an electric vehicle.
 32. A vehicle transmission for driving a vehicle, wherein the vehicle transmission has a pump stage assembly configured to supply a lubricating oil to at least one consumer, comprising: a pump housing; at least two pump suction stages formed by a first external gearwheel assembly of at least three intermeshing external gearwheels that lie in a first plane and configured to: draw in the lubricating oil from a first oil container functioning as a dry sump, and deliver the lubricating oil to a second oil container functioning as an oil tank; and at least one pump pressure stage formed by a second external gearwheel assembly of two intermeshing external gearwheels which lie in a second plane and configured to: draw in the lubricating oil from the second oil container, and deliver the lubricating oil to a consumer, wherein the at least two pump suction stages and the at least one pump pressure stage are arranged spaced apart from one another in the pump housing and have a common drive shaft, wherein the first plane and the second plane lie parallel to one another, wherein at least two respective tooth center points of the first external gearwheel assembly and respective tooth center points of the second external gearwheel assembly are arranged in a common plane that intersects the pump housing in a longitudinal direction and lies orthogonal to the first and second planes. 